Accessibility and selective stabilization of the principal spin states of iron by pyridyl versus phenolic ketimines: modulation of the (6)a(1) <-> t-2(2) ground-state transformation of the [fen4o2](+) chromophore

dc.contributor.author	Shongwe, Musa S.
dc.contributor.author	Al-Zaabi, Usama A.
dc.contributor.author	Al-Mjeni, Faizah
dc.contributor.author	Eribal, Carla S.
dc.contributor.author	Sinn, Ekkehard
dc.contributor.author	Al-Omari, Imaddin A.
dc.contributor.author	Hamdeh, Hussein H.
dc.contributor.author	Matoga, Dariusz
dc.contributor.author	Adams, Harry
dc.contributor.author	Morris, Michael J.
dc.contributor.author	Rheingold, Arnold L.
dc.contributor.author	Bill, Eckhard
dc.contributor.author	Sellmyer, David J.
dc.date.accessioned	2012-09-21T14:51:34Z
dc.date.available	2012-09-21T14:51:34Z
dc.date.issued	2012-08-06
dc.identifier.citation	Shongwe, Musa S.; Al-Zaabi, Usama A.; Al-Mjeni, Faizah; Eribal, Carla S.; Sinn, Ekkehard; Al-Omari, Imaddin A.; Hamdeh, Hussein H.; Matoga, Dariusz; Adams, Harry; Morris, Michael J.; Rheingold, Arnold L.; Bill, Eckhard; Sellmyer, David J. 2012. Accessibility and Selective Stabilization of the Principal Spin States of Iron by Pyridyl versus Phenolic Ketimines: Modulation of the (6)A(1) <-> T-2(2) Ground-State Transformation of the [FeN4O2](+) Chromophore. Inorganic Chemistry, v.51 no.15 pp.8241-8253	en_US
dc.identifier.issn	0020-1669
dc.identifier.other	WOS:000307134700036
dc.identifier.uri	http://dx.doi.org/10.1021/ic300732r
dc.identifier.uri	http://hdl.handle.net/10057/5321
dc.description	Click on the DOI link below to access the article (may not be free).	en_US
dc.description.abstract	Several potentially tridentate pyridyl and phenolic Schiff bases (apRen and HhapRen, respectively) were derived from the condensation reactions of 2-acetylpyridine (ap) and 2'-hydroxyacetophenone (Hhap), respectively, with N-R-ethylenediamine (RNHCH2CH2NH2, Ren; R = H, Me or Et) and complexed in situ with iron(II) or iron(III), as dictated by the nature of the ligand donor set, to generate the six-coordinate iron compounds [Feu(apRen)(2)]X-2 (R = H, Me; X- = ClO4-, BPh4-, PF6-) and [Fe-II(hapRen)(2)]X (R = Me, Et; X- = ClO4-, BPh4-). Single-crystal X-ray analyses of [Fe-II(apRen)(2)] (ClO)(2) (R = H, Me) revealed a pseudo-octahedral geometry about the ferrous ion with the Fe-II-N bond distances (1.896-2.041 angstrom) pointing to the (1)A(1) (d(n)(6)) ground state; the existence of this spin state was corroborated by magnetic susceptibility measurements and Mossbauer spectroscopy. In contrast, the X-ray structure of the phenolate complex [Fe-III(hapMen)(2)]ClO4, determined at 100 K, demonstrated stabilization of the ferric state; the compression of the coordinate bonds at the metal center is in accord with the T-2(2) (d(pi)(5)) ground state. Magnetic susceptibility measurements along with EPR and Mossbauer spectroscopic techniques have shown that the iron(III) complexes are spin-crossover (SCO) materials. The spin transition within the [(FeN4O2)-N-III](+) chromophore was modulated with alkyl substituents to afford two-step and one-step (6)A(1) <-> T-2(2) transformations in [Fe-III(hapMen)(2)]ClO4 and [Fe-III(hapMen)(2)]ClO4, respectively. Previously, none of the X-salRen- and X-sal(2)trien-based ferric spin-crossover compounds exhibited a stepwise transition. The optical spectra of the LS iron(II) and SCO iron(III) complexes display intense d(pi) -> p(pi)* and p(pi) -> d(pi) CT visible absorptions, respectively, which account for the spectacular color differences. All the complexes are redox-active; as expected, the one-electron oxidative process in the divalent compounds occurs at higher redox potentials than does the reverse process in the trivalent compounds. The cyclic voltammograms of the latter compounds reveal irreversible electrochemical generation of the phenoxyl radical. Finally, the H(2)salen-type quadridentate ketimine H2hapen complexed with an equivalent amount of iron(III) to afford the mu-oxo-monobridged dinuclear complex [{Fe-III(hapen)}(2)(mu-O)] exhibiting a distorted square-pyramidal geometry at the metal centers and considerable antiferromagnetic coupling of spins (J approximate to -99 cm(-1)).	en_US
dc.language.iso	en_US	en_US
dc.publisher	AMER CHEMICAL SOC	en_US
dc.relation.ispartofseries	Inorganic Chemistry;v. 51 no.15
dc.subject	Crossover Ferric Complexes	en_US
dc.subject	X-Ray Crystal	en_US
dc.subject	Schiff-Base Complexes	en_US
dc.subject	Magnetic-Properties	en_US
dc.subject	Molecular-Structure	en_US
dc.subject	Coordination Chemistry	en_US
dc.subject	Donor Ligands	en_US
dc.subject	Intermolecular Interactions	en_US
dc.subject	Mossbauer-Spectroscopy	en_US
dc.title	Accessibility and selective stabilization of the principal spin states of iron by pyridyl versus phenolic ketimines: modulation of the (6)a(1) <-> t-2(2) ground-state transformation of the [fen4o2](+) chromophore	en_US
dc.type	Article	en_US
dc.description.version	Peer reviewed
dc.rights.holder	Copyright 2012 American Chemical Society